title: Knockdown of TIGAR by RNA interference induces apoptosis and autophagy in HepG2 hepatocellular carcinoma cells.
abstract: Apoptosis and autophagy are crucial mechanisms regulating cell death, and the relationship between apoptosis and autophagy in the liver has yet to be thoroughly explored. TIGAR (TP53-induced glycolysis and apoptosis regulator), which is a p53-inducible gene, functions in the suppression of ROS (reactive oxygen species) and protects U2OS cells from undergoing cell death. In this study, silencing TIGAR by RNAi (RNA interference) in HepG2 cells down-regulated both TIGAR mRNA (∼75%) and protein levels (∼80%) and led to the inhibition of cell growth (P<0.01) by apoptosis (P<0.001) and autophagy. We demonstrated that TIGAR can increase ROS levels in HepG2 cells. The down-regulation of TIGAR led to the induction of LC-3 II (specific autophagic marker), the formation of the autophagosome, and increased Beclin-1 expression. 3-MA (3-Methyladenine), an inhibitor of autophagic sequestration blocker, inhibited TIGAR siRNA-enhanced autophagy, as indicated by the decrease in LC-3 II levels. Consequently, these data provide the first evidence that targeted silencing of TIGAR induces apoptotic and autophagic cell death in HepG2 cells, and our data raise hope for the future successful application of TIGAR siRNA in patients with hepatocellular carcinoma (HCC).
authors.affiliation: Laboratory of Neuroimmunology and Regenerative Therapy, Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE 68198-5930, USA.
authors.forename: Ling
authors.initials: L
authors.lastname: Ye
authors.forename: Xiaoping
authors.initials: X
authors.lastname: Zhao
authors.forename: Jian
authors.initials: J
authors.lastname: Lu
authors.forename: Guanxiang
authors.initials: G
authors.lastname: Qian
authors.forename: Jialin C
authors.initials: JC
authors.lastname: Zheng
authors.forename: Shengfang
authors.initials: S
authors.lastname: Ge
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D001343:Autophagy; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000473:pathology; D015536:Down-Regulation; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D008113:Liver Neoplasms / Q000235:genetics* / Q000473:pathology; D010744:Phosphoric Monoester Hydrolases; D034622:RNA Interference
chemical_list: D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010744:Phosphoric Monoester Hydrolases; C512708:TIGAR protein, human
keywords: Apoptosis; Autophagy; HCC; Hepatocellular carcinoma; RNA interference; RNAi; ROS; TIGAR; TP53-induced glycolysis and apoptosis regulator; hepatocellular carcinoma; reactive oxygen species; siRNA; siRNA for TIGAR; siTIGAR; small interference RNA